Heritage Essential Oils is by far my favorite resource for essential oils. The gal that runs it, Linda, is a Christian homeschooling mama with a daughter who has Ds. She has graciously posted here what she uses for her daughter, in an effort to help those of us who have children with Down syndrome. Her oils are VERY high quality, the prices are reasonable, and shipping is VERY fast! If I order on Monday, it is in my mailbox in ALASKA on Friday!
I would recommend buying the travel kit first! For $75 you get 16 trial size oils you can try as well as a nice carrying case. I refill the little bottles and keep the kit in the diaper bag! We almost ALWAYS wind up using it. Along with that, I recommend purchasing a big bottle (as big as you can afford) of peppermint AND lavender. We use those the most. I also recommend buying a nice Whisper diffuser when you can fit it into your budget.